Linters! It is all about the linters. Linters analyse your code either in real time or when you would like them to run.
They evaluate your code and let you know if you are not following best practices or if you are making some kind of violation.

While they are great to run here and there, it is best to have them always running through your code editor of choice.
Most code editors have support for packages/modules/plugins/add-ons that allow for you to add the various linters you need.

There are linters for just about every language, variation of a language and more.

Linters will improve your code quality, maybe not 10 fold, it depends on what your code quality is already like, but more than likely you will find something you can be doing better.